The present invention relates to permanent magnet motors.
A motor comprises a multi-pole ring-shaped magnet that rotates relative to a stator. The stator comprises multiple coils toroidally-wound about a ring-shaped core and sequentially disposed along the circumference of the core.
In one embodiment of the invention, an electrical machine comprises a magnetically permeable ring-shaped core centered on an axis of rotation and having two axially-opposite sides. Coils are wound toroidally about the core and disposed sequentially along a circumferential direction of the core. Each coil includes two side legs extending radially alongside respective sides of the core. Coil-free spaces exist between adjacent side legs. A bracket has first and second side flanges that are connected by a bridging structure and respectively abut the first and second sides of the coil.
Preferably, the first side flange is configured to provide a flat side surface defined by the first side flange and the side legs that are adjacent the first side flange. The first side flange has a thickness approximately equal to a bundle thickness of the side legs adjacent the first side flange. The first side flange is formed of plastic. The second side flange of the bracket is like the first side flange. The bridging structure is a flange filling the space between adjacent radially-outer legs of the coils and having a thickness approximately equal to a bundle thickness of the adjacent radially-outer legs.
In another embodiment of the invention, an electrical machine comprises a magnetically permeable core that is elongated to thereby define a lengthwise direction and a profile that is transverse to the lengthwise direction. Coils are wound about the core profile and sequentially disposed along the lengthwise direction. A magnet is adjacent to the core and movable relative to the core. The core includes fragmented magnetically permeable material.
Preferably, the magnet comprises a multi-pole permanent magnet having a surface that is adjacent and facing one of the side surfaces of the core. The core is ring-shaped and centered on an axis of rotation, such that the lengthwise direction is a circumferential direction, the first section is ring-shaped and the second section is ring-shaped and located about the first section. The first section comprises turns of iron-based wire, and the second section comprises spirally wound iron-based tape.
In another embodiment, an electrical machine comprises first and second magnetically permeable parallel cores. Each core is elongated to thereby define a lengthwise direction and first and second core profiles transverse to the lengthwise direction. First coils are wound about the first core profile and sequentially disposed along the length of the first core. Second coils are wound about the second core profile and sequentially disposed along the length of the second core. A multi-pole elongated permanent magnet is parallel with both cores and located between them. The magnet is movable, relative to the cores, in the lengthwise direction.
Preferably, the lengthwise direction extends about an axis of rotation such that the elongated cores are ring-shaped and centered on the axis and the coils are toroidally wound about the cores and sequentially disposed about the axis.
In another embodiment, the machine further comprises a multi-pole ring-shaped permanent magnet centered on the axis. The core and the magnet are disposed one about the other.
A method of making a magnet assembly comprises providing a ring-shaped permanent magnet centered on an axis and having radially inner and outer surfaces and opposite first and second side surfaces. A casing material is overmolded about the magnet to yield a magnet assembly with the casing material located along the radially inner and outer surfaces and the first side surface. A boring location is determined for the particular assembly by performing a balance test on the assembly. An axially-extending hole is bored in the blank at the boring location. A rotor shaft is secured in the hole.
Another method comprises providing a ring-shaped permanent magnet having radially inner and outer surfaces and opposite first and second side surfaces. A casing material is overmolded about the magnet to yield a magnet assembly. The casing material comprises a material that shrinks as it cools from a molten state and being located along the radially and outer surfaces and the first side surface. The assembly is mounted about a rotor shaft.